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Yes Ive got the bug quite bad  it start harmlessly enough looking for a good ECC83 sub & ended with a new tube rectified pre-amp and a host of ECC82 types and some not so close types. A few weeks ago I bought an Eastern Electric MiniMax preamp  a nice simple little unit using 2 x ECC82/12AU7s and a single 6X4. Unfortunately, the designer and the US importer seem to revel in the units ability to be completely tuneable by valve/tube rolling, this is to the extent of being able to use E80CC, 12BH7, 13D5 in place of the normal ECC82/12AU7 substitutes. Also there is a debate about the merits of not using 82s at all but ECC81/12AT7 or 12AY7 or 12AV7 or E180CC ..there is even a website dedicated to these topics and sad to say Ive got more posts on there except the designer of the EE range. Unfortunately, or perhaps fortunately its not used very much as the designer/importers no longer respond proactively to posts.

Well I finally got round to trying out a NOS (1960s) Radiotechnique 6X4 and what a surprise this was. The tube itself is quite different in appearance from the Haltron and GE CV4005 I have. Like those it has the anode plates in a cross shape (if you were to look down on the tube from the top) but at the edge of the plate there is a wide silver plate, so each leg of the cross forms the profile of a T  hope that makes sense. The other major difference is that unlike the Haltron, the tube hardly puts out any light. The Haltron seems to be trying to impersonate a bulb, the GE less so.

Anyway as to the sound, well its got more detail that the Haltron and the GE CV4005, with a clear emphasis or forward presentation in the treble register, which is a big negative for me. Mid-band is sumptuous and all underpinned with a clean and detailed bass. But the really big difference is the speed and dynamic presentation it provides, this tube is (or allows the Pre to be) very, very fast. If youve ever heard a full blown Naim system on song youll know what I mean  Pace, Rhythm & Timing (PRaT) to set your heart racing. But unlike the Naim sound I also have a wide soundstage with good depth and inner clarity and detail. Part of this must be due to the Pre allowing the inherent start/stop prowess of my SME20/2a turntable to shine through; Ive yet to try the CD player, but this is awesome for live jazz. Now if I can only tune out the treble emphasis this is really going to provide long term listening pleasure. The only caveat I would add is that the tube has only had a three hour work-out and Ive found some tube do change their sound or balance  I only hope the treble begins to tone down. But all this from a rectifier and not a signal valve.

Im using the stock tube (Chinese 12AU7) in the buffer stage and an elderly Mullard (ECC82) in the amplification stage.

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Hi Paul...you certainly have got the bug!...I've also tried a wide range of new and NOS tubes in the tube amps I've owned,and like many others,came down heavily in favour of NOS tubes,although you do occasionally get a duffer or 2(as I did with a set of 5687 drivers for my 300B amps....harsh,nasty and compressed,and in no way comparable to a good set of Raytheon 5687s).

A number of people put the differences in rectifiers down to the performance under load,and again some of the NOS ones,esp things like RCA 5U4's do have better performance at the limits than some of the newer alternatives,although the old Svetlana ones are fine.

The nice thing about tube amps is that providing you stick to pin-,and electrically compatible tubes,you can change the sound of your amp quite dramatically and easily,if not cheaply!....do be careful with some of the modern alternatives however,as not all of the pin-outs are totally as per the originals.

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6X4, The CV4005 GEC are great, also look to U78 (older) again made by MOV etc or EZ90, where I like the Mullards. The 6X4 are a great little tube and stock US production is good also especially the 6X4W and 6X4WA but I would be more than happy with a straight 6X4 from one of the big US firms (RCA etc).

Re 5U4G, I think the Tung Sol are the best of the US makes but have seen some excellent performances form the other big US companies (RCA, Westinghouse, CBS, GE etc etc). U52 are worth looking out for here or a slow warm up GZ tube (hard to beat 34 and 37s where applicable). The best of these are the big bulb GZ37 for me (MOV?) which I feel sound much better than even the 'now more often soldstock' GZ37 with it's thinner bulb.

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One of the fundamental differences between this Pre design and many others seems to be that it was built with Tube Rolling in mind. Would you find many pre-amps that you could replace the 12AU7's with E80CC's (drawing twice the current)? But this is considered by the both the designer/distributor (US) to be a good basic change for the buffer stage, although perhaps considered to give a to aggressive sound in the amplification position. Be interesting to see what a pair of these will sound like with the turbo 6X4 in place, then again the 12DH7 and 13D5s also promise some interesting options.

From the user forums the most consistently praised combinations seem to revolve around 1950 tubes; Tung-Sol black glass 12AU7, Amperex 7316 D getter, Hivacs, Gold Lion U707 square getter double getter support and Tung-Sol 6X4WA. This latter one being the only tube I think is readily available at reasonable cost (even if not a 50s tube). Basically I feel that it would be quite ruinous to seek out some of these more esoteric tubes with a set costing as much as the Pre-amp itself. You couldnt just have one of each  youd need some spares, as it would be quite traumatic to get that sound and know that when the tubes expire you may never get another, or if you did, the cost would be prohibitive. Mind you Ill have a few tubes to sell on ebay later, tried and didnt like Telefunken ECC82s, GE CV4005, and so on.

The company also makes a nice little power amp using ECL82s and a GZ34/5AR4 rectifier, a Phono stage using ECC83/12AX7s and 6X4 rectifiers, a CD player using (as they put it) Tubes: 6922 x 2 or any tube like CCa, E88CC, E188CC, ECC88, 6DJ8 and an integrated amp using 12AU7s (phase splitter) Ef86 (1st driver) GZ34/5AR4 (rectifier) and EL34 output tubes. This with class a, Pentode or ultra linear, 3 levels of feedback selection and a remote control.

If I were to get a combination of these units, I feel that the old saying that there is little difference between a hobby and clinically obsessive behaviour, might indeed become true. Mind you that phono-stage looks very tasty.

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If I were to get a combination of these units, I feel that the old saying that there is little difference between a hobby and clinically obsessive behaviour, might indeed become true. Mind you that phono-stage looks very tasty.

Paul

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Definitely go along with that statement...once you get going on things like that it never stops,it just gets more expensive.

The nice thing currently is that there are so many companies around offering well sorted kits,and lots of upgrades...our own WAD,then companies like Wellborne Labs,DIYHifi Supply,and Bottlehead etc etc.

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With the Romulus I purchased, and am running a matched quad of 6L6WGC NOS Russian Military valves from the early 80s. As Im using the separate Pre, I am no longer worried about the 12AX7/ECC83, but did get to try a Mullard ECC83 that was very good. Phase splitters remained CVC branded 12AX7s and for the pre drivers Ive tried Mullard CV4003s, M8136s and Telefunken ECC82s. In the end went back to the CVCs as these in fact turned out to be re-branded US manufactured 5814As and were only bettered by the M8136. Ill go back to looking at these when Ive settled on a combination of valves for the Pre-amp. One of the main reasons for the choice of the Romulus was as a stepping-stone toward seperates, as it had the ability to be use as a power amp.

As to the pre, well its beautifully made, seems inherently neutral and quite tiny, only measuring about 12 X 6 inches, W X D and yes, it does originate from China. It betters (from memory) my previous Audio Research Pre-amp, with far more detailed and lucid sound and I prefer it to the S/H Conrad Johnson Pres Id been considering and was less than half the cost. Several people have been very positive about the unit one replaced his Hovland Pre, another is using it within a system ending with Wilson Grand Slamms  (so Im told) I dont see how it can be considered that good, but think Id end up paying a lot more to get a better Pre. Unfortunately, theres no distributor in the UK, nearest is in Germany. There are a few Pres about, I believe in one UK dealership. I really would like to try out the Phono stage at some point, but I guess this would mean taking a chance and just getting one shipped over un-auditioned, or I suppose it would be an excuse to pop over to Germany for a couple of days. Either way at nearly a £1,000 (and more expensive that the pre) not likely to be happening in a hurry.

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I thought CVC's own branded tubes were made in China? I'm pretty sure mine are. Anyway, I've never really believed the nay-sayers about CVC's. I still think they sound fine.

I see the minimax is seeing-off some very expensive competition there! Will look around on the web for some pictures.

DT

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I was suprised when I compared them on sound quality terms and under magnification you could clearly see the remains of the old tube markings USA 5814A on one and patrtially on the other. I expect CVC rebrand whatever they can get at an economical price

I will say that initially when I received the MM Pre I was less satisfied - soundstage was very big, but the balance seemed wrong - but it's getting there now, plus I've got a fair collection of valves to try, with hundreds of possible combinations

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I was suprised when I compared them on sound quality terms and under magnification you could clearly see the remains of the old tube markings USA 5814A on one and patrtially on the other. I expect CVC rebrand whatever they can get at an economical price

for the German distributor - button to select English at the bottom left of screen.

These pics are of the older model - it now has four inputs.

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I've used Chelmer Valve for many yrs now,and always been happy with the service,and the tubes.
They do use a lot of rebadged Chinese tubes in the lower end of their market,but also have a very large stock of NOS tubes,and usually at pretty decent prices,considering some of the market prices being asked.

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I've used Chelmer Valve for many yrs now,and always been happy with the service,and the tubes.
They do use a lot of rebadged Chinese tubes in the lower end of their market,but also have a very large stock of NOS tubes,and usually at pretty decent prices,considering some of the market prices being asked.

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They have been very helpful and seem to provide reasonable prices, but its still too exspensive just to try the odd valve - yes if you know you want a specific one then no problem (although postage for a single valve is a killer as far as I'm concerned). So ebay it is for the trial tubes, find what I like, then over to Chelmer for some stock. Got 2 NOS Tung-Sol 6X4WA (1960's) in the post but got these from Watford Valves and just received a Philips E80CC, Brimar 13D5, Sylvania 12BH7A, RCA 5814A (black plate) for £7 inc postage to try out. Trouble is I'm now looking at valve testers as well Time to sign up for some counselling therapy

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Trouble is I'm now looking at valve testers as well Time to sign up for some counselling therapy

Paul

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Got an AVO Mk III and an old Mk I here....you should have a look at crowthorne tubes( www.crowthornetubes.com ) and maybe speak to Gerry there....his knowledge of all things relating to them is superb,and he also repairs/refurbishes them,so if you bought a broken one(usually it's the meter that fails),he can advise,and repair.

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The NOS (1960s) Radiotechnique 6X4, Plus Sylvania 12BH7A, plus Mullard ECC82 Box anode (not CV4003 or M8136, these were far to warm) and it sounds, well just oh so right

Soundstage is very wide, depth is palpable and obvious, vocals are sublime, bass is fast, tight and articulate, treble is effortless and measured - enjoyment factor

Can it get any better? Well the 60's Tung-Sol 6X4WA should be here soon (later this morning) so I guess I'll just have to wait and see I'm not sure I'll ever be able to own a solid state amplifier ever again. Well its just past midnight and I'm going to listen to some more, oh and this preamp loves CD, even my old NAD has a new lease of life!

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Now try a 5993 Bendix This baby survives atomic bombs. 6063 GEC is good as well

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Hi Nic

Tried to find some info on the 5993 and couldn't find diddly, put Bendix in the search and got info about a 70's tumble dryer

Actually this now sounds so good I'm going to scale the tube rolling right back although I will be looking for a few 12BH7's as spares. The Tung-Sol 6X4WA, in this set-up, wasn't as good as the Radiotechnique 6X4 (of the same, 60's vintage) So I'll get another couple of these for spares if I can and thats about it. Mind you I did mention I'd go back and have another look at the Power amp section of the Romulus.

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Ah it is just for us in the know, PM me yor address and I will photocopy an article for you

When Tung Sol and RCA were making 6x4 and 6V6GT for 10cc each, Bendix made 5993 for $50 (true, don't know exact figure but basically correct). This is the stuff that went into the like of ICBMs etc and only real competition was really the likes of red base 5691, 5692 and 5693 but to be trueful even these look mickey mouse next to Bendix. Whether it sounds any better.....

At the moment I find the system a bit too 'dry' sounding and not as musically satisfying as I would like, so I'm hoping adding a valve preamp into the chain and bypassing the digital volume control of the DAX will add some warmth and lushness to the sound.

One thing I will say is this Pre seems to really love CD as a source. It also seems to have been manufactured with the concept of tube rolling as a method of fine tuning the sound and character of its influence on the system as a whole. Live with the unit as is for a few weeks before you even decide to try some other tubes and then see what you think needs changing to the character of the sound. I don't know how it will react in conjunction with the Bryston, but I know there have been some very positive reports from other SS power amp users.

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The Minimax is here! What a little beauty it is. The previous owner had fitted it with a Brimar 6x4 and two Mullard EC882, and also gave me the two new unbranded EC822 that originally came with the unit. Since the Brimar and Mullards are already run in I'll start with those.

I know the reputation of the Mullards but is the Brimar 6x4 (EZ90) any good? I don't have anything else to try here.

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The Minimax is here! What a little beauty it is. The previous owner had fitted it with a Brimar 6x4 and two Mullard EC882, and also gave me the two new unbranded EC822 that originally came with the unit. Since the Brimar and Mullards are already run in I'll start with those.

I know the reputation of the Mullards but is the Brimar 6x4 (EZ90) any good? I don't have anything else to try here.

As you can see the Brimar is near the bottom, but that was a CV or mill spec tube, so I suspect yours will be nearer the Mullard in general terms. Based on what I've tried in the past search out a 12BH7 for the centre slot to add a bit more dynamics and widen the sound-stage. Any New Old Stock (NOS) one will be OK in this position - I've not tried any of the current production ones.

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It's the 3-input model. I'm quite pleased with the Minimax so far. It makes the sound through my Bryston/PMC system less aggressive, with an overall warmer tone. The bass seems weaker but is well defined and tight. The overall sound is still a bit lean though so I would appreciate suggestions for valves that might give me a more tubey sound, a bit more full-bodied. I don't know if one of the Mullards is faulty - when powering up, it glows REALLY brightly for 2 or 3 seconds before settling down to a much dimmer level. The other Mullard and the Brimar both light up gently and dimly. I tried swapping the two Mullards around the buffer and amplifer positions which showed the problem is with the valve and not the Minimax. Does it sound like a bad valve?

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It's the 3-input model. I'm quite pleased with the Minimax so far. It makes the sound through my Bryston/PMC system less aggressive, with an overall warmer tone. The bass seems weaker but is well defined and tight. The overall sound is still a bit lean though so I would appreciate suggestions for valves that might give me a more tubey sound, a bit more full-bodied. I don't know if one of the Mullards is faulty - when powering up, it glows REALLY brightly for 2 or 3 seconds before settling down to a much dimmer level. The other Mullard and the Brimar both light up gently and dimly. I tried swapping the two Mullards around the buffer and amplifer positions which showed the problem is with the valve and not the Minimax. Does it sound like a bad valve?

I'm going to try the unbranded ECC82s tomorrow.

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Swapping out the Brimar, for a Tung-Sol 6X4, may give a warmer overall character - this considered by many as a good improvement.

Price seems reasonable (this seller also has some Radiotechnicque 6X4's - I like these a lot they are very fast and dynamic, but have treble emphasis, which is difficult to tame) there are various Getter styles & vintages that are supposed to be better than others - but you could spend a fortune trying them all.

The ECC82 tube flash at start-up is nothing to be concerned about - some do, some don't. I feel this is more prevalent with East European tubes than British or US ones and I would suspect the Mullard may therefore be a re-branded one - perhaps those with more knowledge of "tube law" could chip in with opinions - have a good look at the outside of the tube toward the base for a set of etched digits which identify place and date of manufacture for genuine UK Mullard tubes.

The Brimar 13D5 is probably the most consistent sounding ECC82/12AU7 variant, being warm, smooth and detailed across the whole spectrum. I would advise against trying the often touted E80CC as this will be to aggressive an lean, based on how you describe the sound you are getting. Also, perhaps forget the other favourite I have which is the 12BH7, as this provides scale and drama in spades, but less warmth. As to the weak, but well defined & tight bass, is this just a quantity and not quality issue, you may find this is more satisfying in the long-term, giving the sound more balanced and neutrality.

I would still caution against making too many changes until you've acclimatised to the sound (or lack of) of the MiniMax. I suspect when you put in the other tubes (they should be OEM Eastern Electric branded) you will get a more prominent bass, but compromise the mid-band, this becoming slightly recessed - let me know if this is the case. Try one in the buffer slot with the non-flashing Mullard in the first (gain) slot, then reverse them. Also remember the above observations will always vary from system to system.

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Thanks Paul, that's really helpful. I didn't have time to play with tubes today, but will do in a next couple of days. By the way my Minimax was modded with V-Caps and Hovlands by Tony (Wadia-miester on Zerogain forum), so it probably sounds a bit different from yours even with the same tubes in place.

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Hi DT, it wasn't me! Someone bought it off WM a couple of months ago and sold it to me last week. I only discovered it was WM's when I looked at the previous delivery labels and took a look under the hood to find it jam packed with mods!